adding "extern C" guard

[CheMax-Tag]

I add missing "extern C" guard for some header files.

This can help to stub out the error described in #617 when using the C++ compiler.

I plan to check all the headers and add missing guards if you don't mind.

[JonatanAntoni]

Thanks @CheMax-Tag, may I ask you to update all file versions and dates of files you've touched, please?
I consider this change (it is non-functional) as a patch level one, hence the file versions should be incremented in the third diget.

Cheers,
Jonatan

[ghost]

Please change file versions (increase 3rd digit) and dates in the file headers.

[CheMax-Tag]

Ok. I'm sorry, this is essentially the first request in my practice).

Another question, the date indicated in the copyright should also be updated?
I mean the year, for example, in this lines:

// Copyright (c) 2017-2020 IAR Systems //Copyright (c) 2017-2019 Arm Limited. All rights reserved.

should I change the year to 2021?

[ghost]

Yes, please change the year to 2021.

[CheMax-Tag]

Ok, it's ready.

[JonatanAntoni]

Copyright should state "2020-2021" not just 2021

[JonatanAntoni]

Please change to "2020-2021"

[JonatanAntoni]

Thanks for taking this over and contributing. May I ask you to sqash all your commits into a single one, please?

[CheMax-Tag]

Thanks for taking this over and contributing. May I ask you to sqash all your commits into a single one, please?

Yes, it will take me a while

[CheMax-Tag]

I'm a little confused with branches collapsing commits.
Please understand, forgive.

Correct commit with all changes 38236c1

[JonatanAntoni]

Hi @CheMax-Tag,

no worries. The PR cannot be merged this way. It looks like you introduced a merge commit.
You need to rebase (!) your changes onto the latest develop branch. During rebase you can squash all commits into a single one.

Cheers,
Jonatan

[JonatanAntoni]

Can one of the admins verify this patch?